Which products and versions are affected by CVE-2021-31755?

Affected: Ac11 Firmware (Tenda). The full list is in the CVE brief.

Is CVE-2021-31755 being exploited in the wild?

It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jun 24, 2021.

Is CVE-2021-31755 in the CISA KEV catalog?

Yes. It was added on Nov 3, 2021 with a federal remediation due date of Nov 17, 2021.

Is there a public exploit for CVE-2021-31755?

Public exploit code is available.

Is there a fix for CVE-2021-31755?

Fixed versions are available, including Ac11 Firmware <=02.03.01.104_cn, Ac11 Firmware 02.03.01.104_cn.

How urgently should CVE-2021-31755 be patched?

Brandefense priority: patch immediately, because it is listed as exploited in the wild.

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Vulnerability Intelligence

CVE-2021-31755

Q: What is CVE-2021-31755?

An issue was discovered on Tenda AC11 devices with firmware through 02.03.01.104_CN.

Q: How urgently should CVE-2021-31755 be patched?

Brandefense priority: patch immediately, because it is listed as exploited in the wild.

CriticalExploitedPublic exploit

An issue was discovered on Tenda AC11 devices with firmware through 02.03.01.104_CN.

Published May 7, 2021 · Updated Nov 10, 2025

Key Facts

Patch immediately

CVE-2021-31755 is a critical-severity vulnerability (CVSS 9.8 v3.1) affecting Ac11 Firmware (Tenda).
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jun 24, 2021. Public exploit code is available.
EPSS estimates a 87% probability of exploitation in the next 30 days.
Fixed versions are available, including Ac11 Firmware <=02.03.01.104_cn, Ac11 Firmware 02.03.01.104_cn.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.

CVSS v3.1

9.8

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS (30-day exploit likelihood)

87%

Higher than 99.7% of all scored CVEs

Exploited in the wild

Yes

4 catalog listings

Public exploit code

Available

Proof-of-concept or weaponized module

Get the full CVE-2021-31755 brief as a PDF

Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.

Description

An issue was discovered on Tenda AC11 devices with firmware through 02.03.01.104_CN. A stack buffer overflow vulnerability in /goform/setmac allows attackers to execute arbitrary code on the system via a crafted post request.

Known-Exploited Catalog Listings

Catalog	Added	Remediation due	Ransomware use
CISA KEV	Nov 3, 2021	Nov 17, 2021	Not reported
Industry KEV feed	Jun 24, 2021	Nov 17, 2021	Not reported
CIRCL KEV	Nov 3, 2021	Nov 17, 2021	Not reported
ENISA EUVD	Nov 3, 2021	n/a	Not reported

Required action: Apply updates per vendor instructions.

Affected Products

1 affected entries in total

Product	Affected versions	Fixed in
Ac11 FirmwareTenda	See advisory	02.03.01.104_cn

Patched Releases

Ac11 Firmware

<=02.03.01.104_cn

Timeline

Publicly disclosed
May 7, 2021
Added to Industry KEV feed
Jun 24, 2021
Added to CISA KEV
Nov 3, 2021
Added to CIRCL KEV
Nov 3, 2021
Added to ENISA EUVD
Nov 3, 2021
Last updated
Nov 10, 2025

Weakness Type

CWE-787 Out-of-bounds Write

References

7 more references in the full CVE brief

FAQ

Common Questions.

An issue was discovered on Tenda AC11 devices with firmware through 02.03.01.104_CN.
Affected: Ac11 Firmware (Tenda). The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jun 24, 2021.
Yes. It was added on Nov 3, 2021 with a federal remediation due date of Nov 17, 2021.
Public exploit code is available.
Fixed versions are available, including Ac11 Firmware <=02.03.01.104_cn, Ac11 Firmware 02.03.01.104_cn.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.

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